Administration of mesenchymal stem cells (MSCs) improves the recovery from acute kidney injury (AKI).The mechanism may involve paracrine factors promoting proliferation of surviving intrinsic epithelial cells, but these factors remain unknown. In the current study, we found that microvesicles derived from human bone marrow MSCs stimulated proliferation in vitro and conferred resistance of tubular epithelial cells to apoptosis. The biologic action of microvesicles required their CD44-and ␤1-integrin-dependent incorporation into tubular cells. In vivo, microvesicles accelerated the morphologic and functional recovery of glycerol-induced AKI in SCID mice by inducing proliferation of tubular cells. The effect of microvesicles on the recovery of AKI was similar to the effect of human MSCs. RNase abolished the aforementioned effects of microvesicles in vitro and in vivo, suggesting RNA-dependent biologic effects. Microarray analysis and quantitative real time PCR of microvesicle-RNA extracts indicate that microvesicles shuttle a specific subset of cellular mRNA, such as mRNAs associated with the mesenchymal phenotype and with control of transcription, proliferation, and immunoregulation. These results suggest that microvesicles derived from MSCs may activate a proliferative program in surviving tubular cells after injury via a horizontal transfer of mRNA.

Because information on management and outcome of AML relapse after allogeneic hematopoietic stem cell transplantation (HSCT) with reduced intensity conditioning (RIC) is scarce, a retrospective registry study was performed by the Acute Leukemia Working Party of EBMT. Among 2815 RIC transplants performed for AML in complete remission (CR) between 1999 and 2008, cumulative incidence of relapse was 32% ؎ 1%. Relapsed patients (263) were included into a detailed analysis of risk factors for overall survival (OS) and building of a prognostic score. CR was reinduced in 32%; remission duration after transplantation was the only prognostic factor for response (P ‫؍‬ .003).

In this multicenter retrospective study, the outcomes of 836 patients with myelodysplastic syndrome (MDS) who underwent transplantation with a human leukocyte antigen (HLA)-identical sibling donor were analyzed according to 2 types of conditioning: reduced-intensity conditioning (RIC) in 215 patients, and standard myeloablative (or high-dose) conditioning (SMC) in 621 patients. In multivariate analysis, the 3-year relapse rate was significantly increased after RIC (hazard ratio [HR], 1.64; 95% confidence interval [95% CI], 1.2-2.2; P ‫؍‬ .001), but the 3-year nonrelapse mortality (NRM) rate was decreased in the RIC group (HR, 0.61; 95% CI, 0.41-0.91; P ‫؍‬ .015). The 3-year probabilities of progression-free and overall survivals were similar in both groups (39% after SMC vs 33% in RIC; multivariate P ‫؍‬ .9; and 45% vs 41%, respectively; P ‫؍‬ .8). In conclusion, the lower 3-year NRM after RIC is encouraging, since these patients were older (age > 50 years in 73% RIC vs 28% in SMC, P < .001) and had more adverse pretransplantation variables. However, based on the higher risk of relapse, patients with no contraindications for SMC should not receive RIC outside of prospective randomized trials, which are needed to establish the position of RIC-based transplantation in the treatment of patients with MDS. (Blood. 2006;108:836-846)

Allogeneic hematopoietic stem-cell transplantation remains a potential curative therapeutic option for many older patients with MDS. In this analysis, disease stage at time of transplantation, but not recipient age or the intensity of the conditioning regimens, was the most important factor influencing outcomes.